CN102692271B - Sky visible light images based direct solar radiation intensity measurement method and device - Google Patents
Sky visible light images based direct solar radiation intensity measurement method and device Download PDFInfo
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Abstract
The invention discloses a sky visible light images based direct solar radiation intensity measurement method and device, wherein the method comprises: an image acquisition step: acquiring the sky visible light images at the scheduled time by utilizing an image acquisition device; a high-brightness pixel counting step: searching for high-brightness pixels in the scheduled area of the sky visible light images, and counting the number of the high-brightness pixels; and a radiation intensity counting step: based on the fitting relationship of the number of the high-brightness pixels in the scheduled area of the sky visible light images determined in advance and the direct solar radiation intensity, calculating the direct solar radiation intensity at the scheduled time according to the number of the high-brightness pixels. According to the invention, through fitting and analyzing the relationship between the sky visible light images and the direct solar radiation intensity, a novel method for detecting or measuring the direct solar radiation intensity through an image processing and analyzing mode is provided, which provides a novel selective scheme for measuring the direct solar radiation intensity.
Description
Technical field
The present invention relates to aerological sounding field, relate in particular to a kind of direct solar radiation strength measurement method and device based on sky visible images.
Background technology
Solar radiation is the key factor that affects general circulation and climate change.Direct solar radiation is the important component part of total solar radiation.From observation or take measurement of an angle, direct solar radiation generally includes the radiation on vertical sun surface (approximately 0.5 °, visual angle) and the sun scattered radiation of very narrow annular sky (a ring day scattering) around.To direct solar radiation intensity, the measurement of irradiance in other words has important value in aerological sounding, sun power utilization and other field relevant to solar radiation, so direct solar radiation intensity is the routine monitoring data of meteorological department.
The direct measurement of direct solar radiation intensity at present, is to utilize direct solar radiation table.Direct solar radiation table mainly consists of light-intaking tube, induction pieces and tracking means conventionally.When work, light-intaking tube is aimed at the sun; Induction pieces absorbs direct solar radiation and converts thereof into measurable electric signal; Tracking means also can be followed the tracks of the movement of the sun for supporting light-intaking tube, thereby makes light-intaking tube accurately follow the tracks of and aim at the sun.
For such direct solar radiation table, the small tracing deviation of tracking means will produce larger system deviation.Like this, in order to eliminate the impact of system tracking error, require direct solar radiation table can in real time, quickly and reliably follow the tracks of the sun.This requires highly to tracking means, and operation and maintenance is also very complicated.
Observation and the measurement of number when an application of direct solar radiation table is counterglow.Be that solar radiation shows the most intuitively sunshine.Sunshine time refers to that the sun is at the time number of an actual irradiation in ground, and it is defined as direct solar radiation intensity and meets or exceeds 120W/m
2the summation of that time, take hour is unit, gets a decimal.The regularity of distribution of sunshine time, has important practical significance for rational deployment agricultural production, the construction that plans a city, exploitation tourist resources, design solar power station etc.Because direct solar radiation table can obtain any appointment direct solar radiation intensity constantly, therefore, it can directly be used for Timing measurement direct solar radiation intensity add up sunshine time.
During due to counterglow, the measurement of number does not need to obtain each direct solar radiation intensity accurately constantly, only needs to judge whether direct solar radiation intensity meets or exceeds 120W/m
2this threshold value, so in prior art, also have some not use the sunshine time observation program of direct solar radiation table.
Sunshine time observation instrument based on burning trace method mainly contains dark-tube sunshine recorder and focusing sunshine recorder.This is the observation instrument at sunshine that most domestic meteorological station is used at present.But the traffic observation of dark cartridge type and focusing sunshine recorder be unable to do without manual operation, as heliogramma needs manual manufacture, installation and replacing, sunshine time need to carry out artificial judgment etc. according to sunlight path (or burnt trace), and this makes the automaticity of the type instrument lower.
Sunshine time observation instrument based on actinometry method, except aforesaid beam radia off-balancesheet, also has bimetallic strip sunshine recorder etc.The bimetallic strip that bimetallic strip sunshine recorder adopts is mechanical deformation type element, is subject to the temperature effect impact of expanding and shrinking, and repeatability is poor, and long-time stability are difficult to guarantee, causes the type sensor measurement precision not high.
In addition, the CSD type sun heliograph of Holland Kipp & Zonen company utilizes three electronic light sensing devices to measure total solar irradiance and scattering irradiance, the difference of recycling solar global irradiance and scattering irradiance obtains the direct irradiance of the sun, and the direct irradiance of this sun can be used to statistics and calculates sunshine time.China Meterological Science Research Institute designed a kind of sunshine recorder of integrating sphere principle that utilizes and calculated sunshine time.But due to some shortcomings separately, all fail to be used widely in business.
Summary of the invention
The object of the invention is to provides a kind of brand-new direct solar radiation strength measurement method with a kind of brand-new design, and provides a kind of direct solar radiation strength meter and a kind of sunshine time measuring method based on this direct solar radiation strength measurement method.
The application's basic conception come from present inventor find the sun in sky visible images and around the quantity of high luminance pixel can reflect the size of direct solar radiation intensity.Specifically, the applicant's inventor has analyzed at the direct solar radiation intensity data sequences of long period scope inter-sync observation and corresponding sky Detection Method in Optical Image Sequences.The inventor is surprised to find, the sun and around present obvious monotonically increasing relation between the quantity of the high luminance pixel in certain area and direct solar radiation intensity, and can obtain fitting function with the matching relation between reflection high luminance pixel quantity and direct solar radiation intensity by fitting algorithm in sky visible images.
According to one aspect of the present invention, a kind of direct solar radiation strength measurement method based on sky visible images is provided, comprising:
Image acquisition step: utilize image acquisition equipment to obtain the sky visible images of predetermined instant;
High luminance pixel counting step: search for the high luminance pixel in the presumptive area of described sky visible images, and the quantity of high luminance pixel is counted;
Radiation intensity is calculated step: the quantity of the high luminance pixel based in presumptive area described in predetermined sky visible images and the matching relation between direct solar radiation intensity, according to the quantity of described high luminance pixel, calculate the direct solar radiation intensity of described predetermined instant.
Preferably, described presumptive area can be the sun in described sky visible images and the region in preset range around thereof.
Preferably, described presumptive area can be extended for the central point of the sun image from described sky visible images the border circular areas of predetermined radii.
Preferably, described direct solar radiation strength measurement method can also comprise sun image central point determining step, the position for the central point of described sun image of determining described sky visible images in described sky visible images.
Preferably, in described sun image central point determining step, can be according to elevation angle and the position angle with respect to described image acquisition equipment at the described predetermined instant sun, the position of the central point that calculates described sun image in described sky visible images.
Preferably, described predetermined radii can be 1.1～3 times of the radius of the sun image in described sky visible images, more preferably 1.2～2 times.
Preferably, described high luminance pixel can be more than or equal to the pixel of predetermined gray threshold for gray-scale value in described sky visible images.Preferably, described gray threshold is chosen between 200-255.
Preferably, described matching is closed and is
y=a*e
bx+c
Wherein, y is the quantity of the high luminance pixel in described presumptive area, and x is direct solar radiation intensity, a, and b, c is fitting coefficient.
Preferably, described direct solar radiation strength measurement method also comprises image acquisition equipment regulating step: regulate described image acquisition equipment, make, for the arbitrary direct solar radiation intensity that is less than maximum possible direct solar radiation intensity, in the presumptive area of the described sky visible images that described image acquisition equipment obtains, to comprise non-high luminance pixel.
Preferably, described image acquisition equipment can obtain equipment for full visual field sky visible images, for obtaining full visual field sky visible images.
According to another aspect of the present invention, a kind of direct solar radiation strength meter based on sky visible images is provided, comprising:
Full visual field sky image obtains equipment, for obtaining the full visual field sky visible images of predetermined instant;
Sun image central point computing module, the position for the central point of sun image that calculates described full visual field sky visible images in the sky visible images of the described full visual field;
High luminance pixel counting module, for searching for the high luminance pixel that gray-scale value is more than or equal to predetermined gray threshold take within the scope of the predetermined radii that the central point of described sun image is the center of circle, and counts the quantity of high luminance pixel;
Radiation intensity is calculated module, for the matching relation between the quantity based on predetermined high luminance pixel and direct solar radiation intensity, calculates the direct solar radiation intensity of described predetermined instant according to the quantity of described high luminance pixel.
According to another aspect of the present invention, a kind of sunshine time measuring method based on sky visible images is provided, comprising:
Image acquisition step: utilize image acquisition equipment with a series of sky visible images of predetermined time interval acquiring;
High luminance pixel counting step: for each sky visible images, search for the high luminance pixel in its presumptive area, and the quantity of high luminance pixel is counted;
Sunshine determining step: for each sky visible images, judge whether it indicates sunshine; Wherein, when the quantity of the high luminance pixel of described sky visible images is more than or equal to a high luminance pixel amount threshold, indicate sunshine; When the quantity of the high luminance pixel of described sky visible images is less than described high luminance pixel amount threshold, represent all the time according to;
Sunshine time calculation procedure: according to the size in the described time interval and indicate that the quantity of the sky visible images at sunshine calculates sunshine time.
Preferably, described sunshine time measuring method can also comprise high luminance pixel amount threshold determining step: the quantity of the high luminance pixel based in presumptive area described in predetermined sky visible images and the matching relation between direct solar radiation intensity, according to a predetermined direct solar radiation intensity threshold, calculate corresponding high luminance pixel amount threshold.
Preferably, described presumptive area can be the sun in described sky visible images and the region in preset range around thereof.
Preferably, described presumptive area can be extended for the central point of the sun image from described sky visible images the border circular areas of predetermined radii.
Preferably, described sunshine time measuring method can also comprise sun image central point determining step: for sky visible images described in each, and the position of the central point of definite described sun image wherein in described sky visible images.
Preferably, in described sun image central point determining step, for sky visible images described in each, can be according to elevation angle and the position angle with respect to described image acquisition equipment at the corresponding moment sun of this sky visible images, the position of the central point that calculates described sun image in this sky visible images.
Preferably, described predetermined radii is 1.1～3 times of radius of the sun image in described sky visible images, more preferably 1.2～2 times.
Preferably, described high luminance pixel is the pixel that in described sky visible images, gray-scale value is more than or equal to predetermined gray threshold.Preferably, described gray threshold is chosen between 200-255.
Preferably, described matching is closed and is
y=a*e
bx+c
Wherein, y is the quantity of the high luminance pixel in described presumptive area, and x is direct solar radiation intensity, a, and b, c is fitting coefficient.
Preferably, described image acquisition equipment can obtain equipment for full visual field sky visible images, for obtaining full visual field sky visible images.
Technical scheme of the present invention has following beneficial effect:
(1) the present invention by Fitting Analysis, between visible images and direct solar radiation intensity, set up on high associated, thereby provide a kind of mode of processing and analyzing by image of novelty to survey or measure the method for direct solar radiation intensity.This measurement for direct solar radiation intensity provides a kind of new possibility;
(2) in a kind of preferred implementation of the present invention, by utilizing the sky visible images in the full visual field, can avoid using complicated solar tracking device, also avoided the systematic measurement error being brought by tracking error simultaneously;
(3) measuring method of direct solar radiation intensity of the present invention can be applied in the various fields relevant to direct solar radiation ionization meter, as the measurement of sunshine time without barrier;
(4) measuring method and the sunshine time measuring method due to direct solar radiation intensity of the present invention is mainly that the mode of being processed and being analyzed by image is carried out, and is therefore very suitable for automatically processing by computing machine, can greatly increase work efficiency.
Accompanying drawing explanation
Fig. 1 (a) shows the different full visual field sky visible images of two width with Fig. 1 (b);
Fig. 2 is the calculating schematic diagram of sun image center position in the sky visible images of the full visual field;
Fig. 3 is according to the process flow diagram of the direct solar radiation strength measurement method based on sky visible images of the present invention;
Fig. 4 is an embodiment according to direct solar radiation strength meter of the present invention;
Fig. 5 is according to the process flow diagram of the sunshine time measuring method based on sky visible images of the present invention.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described in more detail.
In basic conception of the present invention, core is the sun and the matching relation between the quantity of high luminance pixel and the direct radiation intensity of the sun around thereof in sky visible images, therefore, below describe first respectively image acquisition step, high luminance pixel counting step and matching step in detail.
image acquisition step
Image acquisition step is to utilize image acquisition equipment to obtain the sky visible images of predetermined instant.The image that includes desirable presumptive area in this sky visible images.Conventionally, the image of this presumptive area refers to the sun and the image in preset range around thereof.
In one embodiment, this image acquisition equipment can obtain equipment for full visual field sky visible images, and as existing various total sky imagers in prior art or full visual field recording geometry, it can obtain the full view visible light image of whole sky substantially.The sky visible images obtaining is like this called full visual field sky visible images.Fig. 1 (a) shows respectively the different full visual field sky visible images of two width with Fig. 1 (b), wherein, in Fig. 1 (a), because cloud layer blocks or other reason, sun image crested; And can obviously see sun image in Fig. 1 (b).
In other embodiments, this image acquisition equipment can be that the local sky visible images of Limited eyeshot obtains equipment, as long as include needed presumptive area in this part sky visible images.The sky visible images obtaining is like this called local sky visible images.For local sky visible images, obtain equipment, it preferably has sun tracker, to follow the tracks of the operation of the sun, thereby in the local sky visible images that can in officely mean regularly to carve, all includes the image of needed presumptive area.
Than local sky visible images, obtain equipment, full visual field sky visible images obtains equipment and can avoid using complicated sun tracker, and further avoids the systematic measurement error that brings due to tracking error.
high luminance pixel counting step
High luminance pixel counting step is the high luminance pixel of wanting in the presumptive area of search the sky visible images, and the quantity of high luminance pixel is counted.For this reason, first need to determine needed presumptive area.As previously mentioned, this presumptive area is the sun and the region in preset range around thereof normally, makes the image of this presumptive area mainly reflect direct radiation and the ring day scattering on sun surface, to can exclude the interference bringing due to reasons such as cloud layer scatterings.
Although this presumptive area can manually be set when sky visible images being carried out to image processing on image, for the ease of robotization, to process, this presumptive area can be preferably that benchmark is set with the central point of the sun image that can calculate.The central point of the sun image on high position in visible images can and utilize various known parameters to calculate according to different image acquisition equipments.For example, when utilizing full visual field sky visible images to obtain equipment to obtain sky visible images, this full visual field sky visible images obtains equipment and conventionally adopts fish eye lens, and the position of the central point of sun image can calculate according to mode shown in Fig. 2.
As shown in Figure 2, the fish eye lens that full visual field sky visible images obtains in equipment is to take towards zenith direction, and the orientation in fish eye images is upper north (N), lower south (S), left east (E), right west (W).O point is that sky withstands on the subpoint in fish eye images, is also the central point of fish eye images, and OD is the imaging radius of fish eye images, and T is the position of the sun in celestial sphere, and P is the imaging point of the sun in fish eye images, the namely central point of sun image.H is sun altitude, and span is 0 ° ~ 90 °.A is the position angle of the sun, and span is-180 ° ~+180 °, and Due South be take to being zero in position angle, by south east northwards for negative, by south orientation west northwards for just.Wherein, elevation angle H and position angle A can utilize the residing longitude of image acquisition equipment, latitude and image imaging Time Calculation to obtain.
At sunrise, sun altitude is zero, and now P point overlaps with D point, and the sun is when top, and sun altitude is 90 °, and P point overlaps with O point, and according to isometric projection principle, the total relation between OP and OD can be expressed as,
Wherein, α is half of fish eye lens visual angle.In conjunction with solar azimuth A, can obtain sunny particular location coordinate in fish eye images and be,
X＝C
x+OD*sinA*(90°-H)/α
Y＝C
y+OD*cosA*(90°-H)/α
Wherein, in formula, X is the horizontal ordinate of solar core in fish eye images, and Y is ordinate, C
x, C
ycoordinate for fish eye images central point.
Although described hereinbefore for adopting fish-eye full visual field sky visible images to obtain a kind of mode how equipment obtains the central point of sun image, but be to be understood that, in other embodiments, also can adopt alternate manner to determine the central point of sun image.In one embodiment, when adopting the mode of the tracking sun to obtain local sky visible images, the central point of this part sky visible images can be considered the wherein central point of sun image.In another embodiment, also can directly to sky visible images, carry out image processing, adopt the mode of image recognition to search for sun image and estimate its center position.
In determining sky visible images after the center position of sun image, can take this center position to set needed presumptive area as benchmark.In one embodiment, this presumptive area is for starting to extend the border circular areas of predetermined radii with the central point of sun image.In one embodiment, the size of this predetermined radii can be by observing and analyze obtained sky visible images or rule of thumb coming manually to preset.In other embodiments, this predetermined radii also can be take the radius of sun image and set as benchmark.For example, this predetermined radii can be 1.1～3 times of sun image radiuses, preferably 1.2～2 times of sun image radiuses.The radius of sun image can manually preset by observing and analyze sun image or rule of thumb coming.Or the radius of sun image also can obtain by the mode of computing machine graphics process, as adopted the mode of image recognition to search for sun image and estimate its radius.For the ease of computing machine, process, it is unit that the radius of aforementioned presumptive area and/or the radius of sun image can be take the number of pixel, at one, be only in exemplary embodiment, sun image radius can be 200 pixels, and the radius of presumptive area can should be 300 pixels mutually.
After having determined needed presumptive area, can to this sky visible images, process with computing machine, in this predetermined areas, search for each pixel, judge whether each pixel is high luminance pixel, and the quantity of high luminance pixel is counted.In this application, high luminance pixel refers to that gray-scale value is more than or equal to the pixel of predetermined gray threshold; Correspondingly, to be less than the pixel of predetermined gray threshold be non-high luminance pixel to gray-scale value.What obtain when image acquisition equipment is during without 8 gray-scale maps of symbol, can set single gray threshold.In one embodiment, this gray threshold can be chosen between 200-255.When image acquisition equipment obtain be coloured image time, can set respectively identical or different gray thresholds for each Color Channel, or can change into a gray-scale map and set a gray threshold.
In a preferred embodiment, high luminance pixel counting step can be completed by computing machine completely automatically.For example, by after sky visible images input computing machine, can this image be analyzed and be processed with computing machine, according to known parameters, calculate the center position of the sun image in sky visible images; Automatic search be take this center position each pixel within the scope of the predetermined radii of the center of circle, and the gray-scale value of each pixel and gray threshold are compared, and take and judges whether each pixel is high luminance pixel, and add up the quantity of high luminance pixel.
matching step
Matching step is used for setting up the quantity of the high luminance pixel in presumptive area in sky visible images and the matching relation between direct solar radiation intensity.
In matching step, can utilize the quantity of the high luminance pixel in the presumptive area of analyzing sky visible images at direct solar radiation intensity data sequences and the corresponding sky Detection Method in Optical Image Sequences of long period scope inter-sync observation and the regression fit relation between direct solar radiation intensity.Direct solar radiation intensity data sequences can obtain by the means of prior art, for example, utilize direct solar radiation table directly to measure.For each sky visible images, the obtaining and can carry out according to the description in aforementioned image acquisition step and high luminance pixel counting step the counting of the quantity of the high luminance pixel in presumptive area wherein of its image.
Like this, after high luminance pixel quantity in obtaining a series of sky visible images and corresponding presumptive area, in conjunction with the direct solar radiation intensity data sequences of synchronization gain, can carry out regression fit analysis to the relation between high luminance pixel quantity and direct solar radiation intensity.Present inventor finds, presents obvious dull nonlinear characteristic between the two.In one embodiment, between the high luminance pixel quantity obtaining and corresponding direct solar radiation intensity, have good exponential relationship, fitting function is as follows:
y=a*e
bx+c
Wherein, y is the quantity of the high luminance pixel in presumptive area in sky visible images, and x is direct solar radiation intensity, a, and b, c is fitting coefficient.
In other embodiments, between the quantity of the high luminance pixel in sky visible images in presumptive area and corresponding direct solar radiation intensity, can be the matching relation of other form, for example the matching relation of polynomial function form.
On the selection of presumptive area in sky visible images and also may affect the concrete form of matching relation to the selection of gray threshold.But, to those skilled in the art, after the direct solar radiation intensity data of the high luminance pixel incremental data in the presumptive area that obtains a series of sky visible images and correspondence, be easy to obtain by fitting algorithm the concrete form that reflects the fitting function of matching relation between the two.
direct solar radiation strength measurement method and device
Fig. 3 shows according to the process flow diagram of the direct solar radiation strength measurement method based on sky visible images of the present invention.
As shown in Figure 3, step 101 is matching step, and it can carry out according to the matching step of describing above, to set up the quantity of the high luminance pixel in the presumptive area of sky visible images and the matching relation between direct solar radiation intensity.
Step 102 is image acquisition step, and it can carry out according to the image acquisition step of describing above, to utilize image acquisition equipment to obtain the sky visible images of predetermined instant.It should be noted that, in step 102, obtain the condition of sky visible images, as the aperture size of image acquisition equipment and time shutter etc., condition preferably and while obtaining sky visible images while carrying out matching in matching step 101 is consistent, to can use the most rightly determined matching relation in step 101 in subsequent step.
Step 103 is high luminance pixel counting step, and it can carry out according to the high luminance pixel counting step of describing above, so that the high luminance pixel in the presumptive area of search the sky visible images, and the quantity of high luminance pixel is counted.It should be noted that in step 103, for the selected of presumptive area and to the judgment criterion of high luminance pixel, should be consistent with setting while carrying out matching in step 101, to use the most rightly determined matching relation in step 101.
Step 104 is radiation intensity calculating step, in this step 104, matching relation based on setting up in advance in step 101, can calculate according to the quantity that obtains high luminance pixel in step 103 the direct solar radiation intensity of described predetermined instant (being the corresponding moment of sky visible images obtaining in step 102).
Here it should be noted that in some cases, when direct solar radiation strength ratio is larger, for example in a certain bigger numerical (as 1000W/m
2) when above, the pixel in the presumptive area of sun visible images may be all high luminance pixel, like this, direct solar radiation strength measurement method of the present invention can be distinguished each direct solar radiation intensity on this numerical value.Therefore, in image acquisition step, preferably image acquisition equipment is adjusted to like this, that is: for the arbitrary direct solar radiation intensity that is less than maximum possible direct solar radiation intensity, in the presumptive area of the sky visible images that image acquisition equipment obtains, comprises non-high luminance pixel.Like this, for arbitrary direct solar radiation intensity level, there is a different high luminance pixel quantitative value corresponding with it.
To the adjusting of image acquisition equipment, can comprise: 1) when imaging, with less aperture and shorter time shutter etc.; Or 2) before camera lens, increase optical filter, adjust light-inletting quantity.
Fig. 4 shows an embodiment of the direct solar radiation strength meter of carrying out this measuring method, and this device can comprise that full visual field sky image obtains equipment, sun image central point computing module, high luminance pixel counting module and radiation intensity and calculates module.Wherein, sun image central point computing module, high luminance pixel computing module and radiation intensity calculating module can be realized by the computing machine (as shown in the empty frame in Fig. 4) that specific program is housed.
Full visual field sky image obtains equipment for obtaining the full visual field sky visible images of predetermined instant.Then, by obtained full visual field sky visible images input computing machine.In computing machine, sun image central point computing module is according to the sun altitude in the moment corresponding to this full visual field sky visible images and the position that the central point of the sun image in this image is calculated at position angle.High luminance pixel counting module take search for this full visual field sky visible images within the scope of the predetermined radii that the central point of sun image is the center of circle in gray-scale value be more than or equal to the high luminance pixel of predetermined gray threshold, and the quantity of high luminance pixel is counted.Radiation intensity is calculated the quantity of module based on predetermined high luminance pixel and the matching relation between direct solar radiation intensity, calculates the direct solar radiation intensity of this predetermined instant according to the quantity of obtained high luminance pixel.
Direct solar radiation strength meter of the present invention can complete the measurement to direct solar radiation intensity automatically.
sunshine time measuring method
Fig. 5 shows according to the process flow diagram of the sunshine time measuring method based on sky visible images of the present invention.
As shown in Figure 5, step 201 is matching step, and it can carry out according to the matching step of describing above, to set up the quantity of the high luminance pixel in the presumptive area of sky visible images and the matching relation between direct solar radiation intensity.
Step 202 is image acquisition step, utilize image acquisition equipment within predetermined time with a series of sky visible images of predetermined time interval acquiring.For each sky visible images, can carry out according to the image acquisition step of describing above.It should be noted that, in step 202, obtain the condition of sky visible images, as the aperture size of image acquisition equipment and time shutter etc., condition preferably and while obtaining sky visible images while carrying out matching in matching step 201 is consistent, to can use the most rightly determined matching relation in step 201 in subsequent step.
Step 203 is high luminance pixel counting step, searches for the high luminance pixel in the presumptive area of each sky visible images, and the quantity of high luminance pixel is counted.For each sky visible images, can carry out according to the high luminance pixel counting step of describing above.It should be noted that, in step 203, for the selected of the presumptive area of each sky visible images and to the judgment criterion of high luminance pixel, should be consistent with setting while carrying out matching in step 201, to use the most rightly determined matching relation in step 201.
Step 204 is determining steps at sunshine, for judging whether each sky visible images indicates sunshine.For a sky visible images, when the quantity of resulting high luminance pixel in step 203 is more than or equal to predetermined high luminance pixel amount threshold, this sky visible images indicates sunshine; When the quantity of resulting high luminance pixel in step 203 is less than this high luminance pixel amount threshold, this sky visible images represent all the time according to.Here, high luminance pixel amount threshold corresponds to a direct solar radiation intensity threshold.Conventionally, in meteorological field, direct solar radiation intensity in other words irradiance meets or exceeds 120W/m
2time for there being sunshine, be less than 120W/m
2time represent all the time according to, therefore can be by 120W/m
2as direct solar radiation intensity threshold.According to this direct solar radiation intensity threshold, and the matching relation based on definite in step 201, can calculate corresponding high luminance pixel amount threshold.
Step 205 is sunshine time calculation procedure, according to the size in the time interval of setting in step 202 and indicate that the quantity of the sky visible images at sunshine calculates sunshine time.In one embodiment, can will in obtain a series of sky visible images, indicate that the moment at sunshine is designated as 1, all the time according to the moment be designated as 0, form a discrete information sequence at sunshine.In accumulation information sequence at sunshine, all 1 number of times occurring, is multiplied by this number of times the time interval of setting in step 202, can obtain the sunshine time of the time range setting in step 202.Time range in step 202 is set as comprising from sun to sun whole when the duration, can calculate the sunshine time of whole day.
The measurement of number when sunshine time measuring method of the present invention can utilize computing machine automatically to complete counterglow.
Claims (10)
1. the direct solar radiation strength measurement method based on sky visible images, comprising:
Image acquisition step: utilize image acquisition equipment to obtain the sky visible images of predetermined instant;
Sun image central point determining step, the position for the central point of sun image of determining described sky visible images in described sky visible images;
High luminance pixel counting step: search for the high luminance pixel in the presumptive area of described sky visible images, and the quantity of high luminance pixel is counted; Wherein, described presumptive area is the border circular areas of the central point extension predetermined radii of the sun image from described sky visible images;
Radiation intensity is calculated step: the quantity of the high luminance pixel based in presumptive area described in predetermined sky visible images and the matching relation between direct solar radiation intensity, according to the quantity of described high luminance pixel, calculate the direct solar radiation intensity of described predetermined instant.
2. direct solar radiation strength measurement method according to claim 1, is characterized in that, described presumptive area is the sun and the region in preset range around thereof in described sky visible images.
3. direct solar radiation strength measurement method according to claim 1, it is characterized in that, in described sun image central point determining step, according to elevation angle and the position angle with respect to described image acquisition equipment at the described predetermined instant sun, the position of the central point that calculates described sun image in described sky visible images.
4. direct solar radiation strength measurement method according to claim 1, is characterized in that, described predetermined radii is 1.1～3 times of radius of the sun image in described sky visible images.
5. direct solar radiation strength measurement method according to claim 4, is characterized in that, described predetermined radii is 1.2～2 times of radius of the sun image in described sky visible images.
6. direct solar radiation strength measurement method according to claim 1, is characterized in that, described high luminance pixel is the pixel that in described sky visible images, gray-scale value is more than or equal to predetermined gray threshold.
7. direct solar radiation strength measurement method according to claim 6, is characterized in that, described gray threshold is chosen between 200-255.
8. according to the direct solar radiation strength measurement method described in any one in claim 1-7, it is characterized in that, described matching is closed and is
y＝a*e
bx+c
Wherein, y is the quantity of the high luminance pixel in described presumptive area, and x is direct solar radiation intensity, a, and b, c is fitting coefficient.
9. direct solar radiation strength measurement method according to claim 1, it is characterized in that, also comprise image acquisition equipment regulating step: regulate described image acquisition equipment, make, for the arbitrary direct solar radiation intensity that is less than maximum possible direct solar radiation intensity, in the presumptive area of the described sky visible images that described image acquisition equipment obtains, to comprise non-high luminance pixel.
10. the direct solar radiation strength meter based on sky visible images, comprising:
Full visual field sky image obtains equipment, for obtaining the full visual field sky visible images of predetermined instant;
Sun image central point computing module, the position for the central point of sun image that calculates described full visual field sky visible images in the sky visible images of the described full visual field;
High luminance pixel counting module, for searching for the high luminance pixel that gray-scale value is more than or equal to predetermined gray threshold take within the scope of the predetermined radii that the central point of described sun image is the center of circle, and counts the quantity of high luminance pixel;
Radiation intensity is calculated module, for the matching relation between the quantity based on predetermined high luminance pixel and direct solar radiation intensity, calculates the direct solar radiation intensity of described predetermined instant according to the quantity of described high luminance pixel.
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